1. Field of the Invention
The present invention relates to a process and an apparatus for continuously reacting liquid alkylene oxide with a liquid substance comprising an organic compound with one or more active hydrogen atoms and a catalyst selected from alkali metal hydroxides and alkali metal alcoholates, hereinafter also referred to as the “liquid catalyzed raw material”, in a reactor selected from    (a) a tubular reactor comprising at least one reaction tube providing a reaction space inside of said tube, and    (b) an annular-gap reactor comprising an outer tube and an inner tube, longitudinally inserted into said outer tube, which form an annular reaction gap extending between the inner of the outer tube, which forms the outer boundary of the reaction gap, and the outer surface of the inner tube, which forms the inner boundary of the reaction gap.
2. Description of Related Art
DE 735 418 discloses a process, wherein a tube reactor comprising one reaction tube is used for a continuous alkoxylation of organic hydroxyl compounds, in particular alkyl phenols, and to a mixture of sodium hydroxide and said organic hydroxyl compound in parts at more than one location along the reaction tube. The distance of the locations for adding the liquid alkylene oxide from one another and the quantity of alkylene oxide supplied at the single locations is chosen such that the reaction temperature can be kept low enough, so that the reaction temperature in the tube does not significantly rise above 200° C. and undesired side reactions can be avoided. In case of working the process e.g. with two feeding locations for alkylene oxide, the organic hydroxyl compound is mixed with about one half of the total required amount of liquid alkylene oxide and the mixture is supplied with a high-pressure pump into a first section of the tube for reaction. After passing said first section, the reaction product is removed from the streaming tube and, after intermediate cooling, mixed with the remaining quantity of the required liquid alkylene oxide and this mixture is supplied with a further high-pressure pump to a second section of the streaming tube and is further reacted to the final product in said section which is then removed. The disclosed process however has many disadvantages including, in particular, that a reactor tube of 200 meter length is required, high pressures over 100 bar have to be maintained in the reaction tube in order to avoid an immediate vaporization of the supplied alkylene oxide and the quantity of alkylene oxide supplied at each feeding location has to be controlled by separate mass flow controllers. Furthermore, this reactor can only be used on a pilot plant scale where the use of a single reaction tube is sufficient, whereas the use of a bundle of reaction tubes, as required for production purposes, would require a multitude of alkylene oxide inlets in each reaction tube of the bundle, each with a mass flow controller. These technical efforts for controlling the alkoxylation are so expensive, that this process has never achieved acceptance in industrial practice.
DE 10054462 describes a similar continuous alkoxylation method, wherein relatively small quantities of liquid ethylene oxide are fed into a tubular reactor or in a tube bundle reactor at a large number of different locations along of the reaction tube (in the Example of this document e.g. at 15 locations). Feeding many small quantities of alkylene oxide is required in order to avoid a runaway of the reactor caused by uncontrolled reaction of the ethylene oxide at the feeding points because of the slow mixing speed of the reactants and the common cooling of all sections along the reaction tube which does not allow a specific control of the temperature in each section. In addition, this process design has again the disadvantage that the alkylene oxide flow is to be measured separately for each feeding location.
US 2008/0306295 claiming the priority of DE102005060816 describes a continuous multi-step process which is specifically designed for carrying out rapid, highly exothermic reactions between a gaseous and a liquid reactant, in particular for reacting a SO3/air mixture with liquid organic compounds including, among several other compounds, alkyl phenols and their alkylene oxide derivatives. The reaction is performed in a reactor selected from
(a) a tubular reactor comprising at least one reaction tube providing a reaction space inside of said tube, and
(b) an annular-gap reactor comprising an outer tube and an inner tube, longitudinally inserted into said outer tube, which form an annular reaction gap extending between the inner surface of the outer tube, which forms the outer boundary of the reaction gap, and the outer surface of the inner tube, which forms the inner boundary of the reaction gap,which reactor (a) or (b) is a thin layer falling-film reactor and is connected with a source of a gaseous SO3/air mixture, wherein    (1) the gaseous SO3/air mixture is supplied to said reactor via a single inlet socket and the SO3/air mixture is split before entering the reaction space or gap into a first and second part    (2) said first part of the SO3/air mixture enters the reaction space or gap of said reactor (a) or (b) at a first location,    (3) the liquid organic compound is supplied as a film onto the inner surfaces of the at least one reaction tube of the tubular reactor (a) or onto the inner surface of the outer tube and/or onto the outer surface of the inner tube of the annular gap reactor (b) at a second location of the reactor, located downstream of said first location, and is brought into contact with the gaseous SO3/air mixture to form a liquid film of the reaction mixture of said reactants moving downstream on said surfaces towards the end of the reactor, and    (4) the SO3/air mixture enters the reactor at said first location over the entire-cross sectional area of the reaction space or gap at said location, and    (5) said second part of the SO3/air mixture is split off at said first location and is channeled from said first location to a third location in the reaction space or gap through a tube in case of a tube reactor (a) or through a double tube, respectively, in case of an annular gap reactor (b), which tube or double tube is inserted into the reaction space or gap, extends from said first location to said third location of the reactor space or gap, respectively, and has a diameter being smaller than the inner diameter of said reaction tube or outer boundary of said reaction gap, thus leaving a reaction space between the outer surface of said tube or double tube, respectively, on one side, and the inner surface of the reaction tube or the outer boundary of the reaction gap, respectively, on the other side,    (6) said third location is located downstream of said second location,    (7) said second part of the SO3/air mixture enters the reaction space or gap of the reactor at said third location and is brought into contact at said third location with the liquid film of the reaction mixture moving downstream on said surfaces towards the end of the reactor and reacts with it on its way to the outlet of the reactor to form the final reaction product.
The disclosed tube reactors have a length of about 10 m (tube diameter 1 inch) and the disclosed ring gap reactors have a length of about 2 m (6.5 mm annular gap width). Whereas reactors of such a length are useful for reacting organic hydroxyl compounds with the very reactive SO3 gas, they have generally been considered to be much too short for reaction of such compounds with liquid alkylene oxides which are much less reactive than SO3 gas.